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Wednesday, 24 October 2012

Developmental coordination disorder (DCD) is a surprisingly common problem; it's thought that 6-8% of school aged children are diagnosable. DCD is a motor disorder, where children have great difficulty in producing skilled actions, especially anything requiring fine motor control. Handwriting, tying your shoelaces, sports of any kind are all huge problems for these children.
One key question about DCD is why does it occur. Part of the problem in answering this is that it is a behavioural diagnosis; you get diagnosed if you have severe motor impairments that aren't a known side effect of something else. Regardless, there are two basic ways in which children might end up with such problems; crudely, they might have difficulties in producing movements, or they might have difficulty learning movements. My colleague and author on this paper, Mark Mon-Williams, uses the analogy that children with DCD may be bad drivers of perfectly working cars or good drivers of malfunctioning cars. It's obviously a little messier than that, but this is the essential idea, and the answer has implications for the kind of interventions you'll try and design.

Tuesday, 16 October 2012

Sabrina has been working on a series of posts on an ecological analysis of language (here, here and here, plus more on the way). Her focus has been on the nature of the information for language, and the similarities and differences this information has with the information for perception. We're working some of this analysis into a paper, and writing that got me thinking about this in a little more detail.Our main move on language is to reject the assumption that language is a qualitatively different kind of task than perception & action. The goal is to find ways to talk about these behaviours using the same basic analysis tools. Part of that is to draw the analogy to how perceptual information gets its meaning and use that to describe how linguistic information gets its meaning. What I want to do here is just map this analogy out a little, because I ended up in an interesting place and I want feedback from people who know more than us on this about whether this is just plain crazy. In particular, if you know anything about the relationship between neural dynamics and the dynamics of speech, we think this is going to be relevant!

Events in the world create information. When a car moves towards you, for example, there are sounds coming from the engine, and the way these sounds change over time is information about the heading of the car. If it's getting louder over time, it's coming towards you; but if the pitch is decreasing at the same time, then the car is going to pass you, not hit you. Increasing volume and constant pitch, however, specifies a collision and the particular rate of change of these variables tells you about the time-to-contact. These patterns of change over time in the acoustic array are related to the way the car is moving via the laws of physics and are therefore informative about the details of the car's motion. Importantly, the relationship between these patterns is also governed by the laws of physics; increasing volume and constant pitch only go together when the car is really heading towards you, for example.

Every perceptual system has limits, though, and those limits are called thresholds. When a stimulus is outside a threshold (e.g. too quiet, or too high pitched) the perceptual system won't respond to it. The problem with electric cars is that they are quiet at
low speeds, and so the variation in pitch you need to detect a collision is small
and possibly below threshold. You could make the cars louder, but this goes against one of the selling points of the cars - reduced noise pollution. Mark suggested creating an artificial sound, an illusion, in which the range of the variation in pitch created by the slowly moving car is amplified without just making the car louder.This is in principle possible, but it's a problem because it's breaking the law, and you end up with less information about the car than when you started.

Friday, 5 October 2012

It's been a while since we've blogged; it's been a crazy summer and we've been insanely busy, but things are settling back down. We have a lot planned for the blog, there's much work to be done on a variety of topics in perception, action, embodied cognition and language. First I want to get back on track with my specification project, so that maybe this can start to move forward.

*****************************I've been reviewing work that has been undermining the concept of specification in perception. Specification is the idea that the information we detect and use to control our behaviour maps 1:1 with some action-relevant property in the world, and the idea that this is even possible is one of Gibson's key contributions to psychology. Rob Withagen, along with Tony Chemero (hence W&C) have reason to believe that specification is actually too high a bar, and that individual variation in perceptual ability makes it likely that different people will use different, often non-specifying information to solve the same task. This variation is highly likely to be present, because that's kind of how evolution works, and they cite various studies (in collision judgements and dynamic touch) that seem to empirically confirm that this variation exists and the fact that it doesn't go away with fairly extensive practice.

Ecological psychologists insist on specification for a reason: the idea of direct perception seems to require it. Direct perception is Gibson's hypothesis that we perceive the world directly in terms of our ability to act on it, without needing internal mental gymnastics to figure out what is going on. Turvey, Shaw, Reed and Mace (1981) proposed that, in order for this to work, perceptual information had to be generated by lawful processes that produced one and only one information variable per property of the world, and that perception required the organism to detect that one variable. Anything less, and it's not clear how the organism can count on having detected the right property in the world without some internal states tracking probabilities and correlations.

Withagen and Chemero think that a) evolution demands a less strict policy for perception to work, b) that there is individual variation, that c) this all shows that specification, while possible, is not required for perception (no 1:1 between world and optics or between the optics and perceiver) but that d) perception can still be direct, just on a continuum - the organism has varying degrees of successful contact with properties in the world, rather than the all-or-none contact implied by the Turvey et al analysis. In one respect, they are throwing out the baby and the bathwater but claiming this still lets them have their cake and eat it too. It's exciting if true, but while I think the fact of individual variation needs to be addressed, I'm not yet convinced by the data or the theory and I think there's more to do. Here are some initial thoughts in that direction.

These thoughts are designed to lead to real science, and if you want in, let us know. Sabrina and I are very interested in the basic question of how information gets it's meaning - Sabrina'slanguageanalyses, for example, depend critically on being able to find a way to have ecological style information in a domain where specification can't possibly work. I've been chatting to Tony and Rob about this work and I'm keen to collaborate: but Sabrina and I are interested in developing broad collaborations to go after this stuff from as many angles as possible, including neuroscientifically. The goal here is to develop and propose grants and experiments - we'll worry about access to equipment later, let's first figure out what we need.

We also want this to bring ecological researchers together, not be yet another schism. Rob suggested in an email that I simply put all this in a paper and we could argue back and forth in the literature. I may yet write that paper, just for the record, but I think we can cut through the "talking past each other" bit much faster here on this blog. I would much rather just crack on with a research programme that
involves multiple labs all pulling in the same direction for a change.